Microbial electrosynthesis of methane and acetate—comparison of pure and mixed cultures

Abstract

The electrochemical process of microbial electrosynthesis (MES) is used to drive the metabolism of electroactive microorganisms for the production of valuable chemicals and fuels. MES combines the advantages of electrochemistry, engineering, and microbiology and offers alternative production processes based on renewable raw materials and regenerative energies. In addition to the reactor concept and electrode design, the biocatalysts used have a significant influence on the performance of MES. Thus, pure and mixed cultures can be used as biocatalysts. By using mixed cultures, interactions between organisms, such as the direct interspecies electron transfer (DIET) or syntrophic interactions, influence the performance in terms of productivity and the product range of MES. This review focuses on the comparison of pure and mixed cultures in microbial electrosynthesis. The performance indicators, such as productivities and coulombic efficiencies (CEs), for both procedural methods are discussed. Typical products in MES are methane and acetate, therefore these processes are the focus of this review. In general, most studies used mixed cultures as biocatalyst, as more advanced performance of mixed cultures has been seen for both products. When comparing pure and mixed cultures in equivalent experimental setups a 3-fold higher methane and a nearly 2-fold higher acetate production rate can be achieved in mixed cultures. However, studies of pure culture MES for methane production have shown some improvement through reactor optimization and operational mode reaching similar performance indicators as mixed culture MES. Overall, the review gives an overview of the advantages and disadvantages of using pure or mixed cultures in MES. Key points • Undefined mixed cultures dominate as inoculums for the MES of methane and acetate, which comprise a high potential of improvement • Under similar conditions, mixed cultures outperform pure cultures in MES • Understanding the role of single species in mixed culture MES is essential for future industrial applications

Review and Perspectives of Emerging Green Technology for the Sequestration of Carbon Dioxide into Value-Added Products: An Intensifying Development

“…As a result, we determined that mixed culture systems performed significantly better than pure culture systems, with production rates varying by up to 2-fold. Major characteristics of mixed cultures provide various benefits over pure cultures, including the ability to be more adaptable and robust, use a wider range of low-cost substrates, and achieve greater productivity rates via synergistic interactions. , Another feature of mixed cultures is their propensity to build biofilms on biocompatible surfaces …”

“…Major characteristics of mixed cultures provide various benefits over pure cultures, including the ability to be more adaptable and robust, use a wider range of lowcost substrates, and achieve greater productivity rates via synergistic interactions. 188,189 Another feature of mixed cultures is their propensity to build biofilms on biocompatible surfaces. 190 2.2.1.3.…”

Making chemicals from the air: the new frontier for hybrid electrosyntheses in artificial tree-like devices

“…However, more detailed studies are necessary. There are also possible alternatives, from microbial electrosynthesis (MES), 206,207 as also commented later, to new solutions that have to be validated more extensively, such as the piezoelectric reduction of CO 2 to acetate with 100% selectivity by SnS nanobelts. 208 A high efficiency in solar-to-acetate conversion from CO 2 through MES coupled with stable photoanode has been reported.…”

Advanced Electroanalysis for Electrosynthesis

“…The growth of mixed cultures on the electrode has shown to be beneficial for bioelectrocatalysis and under same conditions, and mixed cultures often outperform pure cultures. 338 The presence of different species renders the biofilm more resilient to environmental stressors and fluctuations, making it more adaptable to different working conditions. In mixed cultures, syntrophic interactions between different organisms can be observed.…”